l-Amino Acid Production by a Immobilized Double-Racemase Hydantoinase Process: Improvement and Comparison with a Free Protein System

Protein immobilization is proving to be an environmentally friendly strategy for manufacturing biochemicals at high yields and low production costs. This work describes the optimization of the so-called “double-racemase hydantoinase process,” a system of four enzymes used to produce optically pure l-amino acids from a racemic mixture of hydantoins. The four proteins were immobilized separately, and, based on their specific activity, the optimal whole relation was determined. The first enzyme, d,l-hydantoinase, preferably hydrolyzes d-hydantoins from d,l-hydantoins to N-carbamoyl-d-amino acids. The remaining l-hydantoins are racemized by the second enzyme, hydantoin racemase, and continue supplying substrate d-hydantoins to the first enzyme. N-carbamoyl-d-amino acid is racemized in turn to N-carbamoyl-l-amino acid by the third enzyme, carbamoyl racemase. Finally, the N-carbamoyl-l-amino acid is transformed to l-amino acid by the fourth enzyme, l-carbamoylase. Therefore, the product of one enzyme is the substrate of another. Perfect coordination of the four activities is necessary to avoid the accumulation of reaction intermediates and to achieve an adequate rate for commercial purposes. The system has shown a broad pH optimum of 7–9, with a maximum activity at 8 and an optimal temperature of 60 °C. Comparison of the immobilized system with the free protein system showed that the reaction velocity increased for the production of norvaline, norleucine, ABA, and homophenylalanine, while it decreased for l-valine and remained unchanged for l-methionine

Tautomeric Equilibria Studies by Mass Spectrometry

Tautomerism in organic chemistry has been extensively studied in condensed phase by spectrometric methods, mainly by IR and NMR techniques. Mass spectrometry studies start 40 years ago but just recently it has been recognized the importance of the mass spectral data for the study of tautomerism in the gas phase.
Mass spectrometry can provide valuable information in regard to tautomeric equilibria when studying mass spectra among the members of different families of organic compounds.
The relevance of the mass spectral data resides on several facts but there are two that are of key importance:
1-	Mass spectral fragmentation assignments should be tautomer specific since the corresponding abundances ratios are supposed to be correlated to the keto/enol contents.
2-	Ionization in the ion source is supposed to have no effect on the position of the equilibrium so that the results reflect the tautomers content in the gas phase previous to ionization.
Some of the carbonylic compounds do not exhibit noticeable tautomerism so the fragment abundances assigned to the enol form is very low or not measurable. Since enolization is more noticeable in the case of thio-derivatives (which correlates adequately with the oxygenated analogues), the study of their mass spectra is an interesting choice to reach some degree of generalization. 
In addition, experimental findings are supported by semiempirical theoretical calculations, which probed to be adequate not only for supporting tendency correlations among the members of a compound family but also to calculate heats of tautomerization in gas phase.
Reports using mass spectrometry for tautomerism are becoming less common. One of the reasons is that now it would appear that the interpretation of MS results is not as straightforward as it was once believed, even though in a recent review it was written that: “Mass spectrometry is the most informative and practical method for studying and identifying tautomers in the gas phase” [1]. 
In fact, mass spectrometry seems to be very informative for studying and identifying tautomers, because in this case external factors like solvents, intermolecular interactions, etc., can be excluded by transferring the tautomeric system into gas phase, where the process becomes truly unimolecular [1].
This review covers the study of Tautomerism by Mass Spectrometry in the last four decades. 
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Hydantoin derivatives of L- and D-amino acids: synthesis, antiviral and antitumoral activity evaluations

3, 5-Disubstituted hydantoin (1, 3-imidazolidinedione) derivatives 5a-h were prepared by base induced cyclization of the corresponding N-(1-benzotriazolecarbonyl)-L- and D-amino acid amides 4a-h. Compounds 5a-h were evaluated for their cytostatic and antiviral activities. Among all the compounds evaluated, 3-benzhydryl-5-isopropyl hydantoin (5a) showed a weak but selective inhibitory effect against vaccinia virus (EC50 = 16 g/mL ; selectivity index: 25). 3-Cyclohexyl-5-phenyl hydantoin (5g) showed inhibitory activity against cervical carcinoma (HeLa, IC50 = 5.4 M) and breast carcinoma (MCF-7, IC50 = 2 M), but also cytotoxic effects towards human normal fibroblasts (WI 38). On the contrary, the 3-benzhydryl-5-phenyl substituted hydantoin derivative 5h showed moderate inhibitory activity towards HeLa, MCF-7, pancreatic carcinoma (MiaPaCa-2), lung carcinoma (H 460) and colon carcinoma (SW 620) (IC50 = 20 23 M), but no effect on WI 38

Hydantoins Derived from Ketopinic and 4-camphorcarboxylic Acids

Diastereospecific formation of hydantoins from ketopinic and 4-camphorcarboxylic acids under Bucherer-Bergs reaction conditions has been investigated. The easiness of this transformation provides a straightforward synthetic pathway to enantiopure conformationally rigid amino acids derivatives, as well as functionalized hydantoins, starting from inexpensive and easily available natural camphor

Revisiting the SAR of the antischistosomal aryl hydantoin (Ro 13-3978)

The aryl hydantoin 1 (Ro 13-3978) was identified in the early 1980s as a promising antischistosomal lead compound. However, this series of aryl hydantoins produced antiandrogenic side effects in the host, a not unexpected outcome given their close structural similarity to the antiandrogenic drug nilutamide. Building on the known SAR of this compound series, we now describe a number of analogs of 1 designed to maximize structural diversity guided by incorporation of substructures and functional groups known to diminish ligand-androgen receptor interactions. These analogs had calculated polar surface area (PSA), measured LogD7.4, aqueous kinetic solubility, and estimated plasma protein binding values in ranges predictive of good ADME profiles. The principal SAR insight was that the hydantoin core of 1 is required for high antischistosomal activity. We identified several compounds with high antischistosomal efficacy that were less antiandrogenic than 1. These data provide direction for the ongoing optimization of antischistosomal hydantoins

Synthesis and spectroscopic characterization of cyclobutyl hydantoins

The hydantoin moiety has proved to be an important pharmacophore that confers a wide range of biological properties to different derivatives. Thus, synthetic methods have been developed to obtain such molecules. Herein, we describe the heterocyclization process to obtain imidazolidine-2,4-diones (hydantoin compounds) from methylcyclobutyl ketones and cyclobutanones derived from (−)-(1S)-α-pinene and (−)-(1S)-verbenone through the Bucherer-Berg reaction. The methylcyclobutyl hydantoins and the spirohydantoin obtained were fully characterized, determining their absolute stereochemistry by nuclear magnetic resonance experiments and theoretical calculations.Fil: Caturelli Kuran, Juan Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Martini, Maria Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Fabian, Lucas Emanuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Moltrasio, Graciela Yolanda. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; ArgentinaFil: Moglioni, Albertina Gladys. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; Argentin

Design, Synthesis, and Evaluation of Aryl Hydantoins and Ureas as Antischistosomal Agents

Schistosomiasis is a tropical parasitic disease caused by infections with flukes of the genus Schistosoma, affecting as many as 440 million individuals worldwide, with 779 million living at risk of infection. A new drug for schistosomiasis is urgently needed as praziquantel (PZQ) is currently the drug of last resort and the development of resistance cannot be ignored, particularly in view of its large-scale use in many endemic countries. Furthermore, PZQ is active against adult but not juvenile schistosomes; this may be an important factor in the frequently observed treatment ‘failures’ in areas endemic for schistosomiasis. The introduction of PZQ in 1982 likely led to decisions to abandon the development of a number of promising antischistosomal agents that were discovered in the same time period. One of these was AH01, the lead compound from a series of aryl hydantoins that were investigated in some detail at Hoffmann La-Roche. A number of characteristics of AH01 justify it as a compelling antischistosomal prototype. This work confirmed the high antischistosomal efficacy of AH01 and demonstrated that the aryl hydantoin is also effective against juvenile infections. Further, AH01 had no measurable interaction with the androgen receptor in a ligand competition assay, but it did block DHT-induced cell proliferation in androgen-dependent cell line. Building on this foundation, a number of AH01 analogs were designed and synthesized to maximize structural diversity guided by incorporation of substructures and functional groups known to diminish ligand-AR interactions. This work identified several new derivatives of AH01 with high antischistosomal efficacy that were less antiandrogenic than AH01. These data provide direction for the ongoing optimization of antischistosomal hydantoins. We also discovered that urea carboxylic acid UC00, the hydrolysis product of AH01, and AR33, a side-reaction product formed in the synthesis of the aryl hydantoins, have substantial in vivo antischistosomal efficacy. Based on this finding, new urea carboxylic acids and N,N\u27-diaryl ureas were designed and synthesized. The most promising compound identified in this work was N,N’-di(quinoxalin-2-yl)urea. This new lead compound can serve as a new direction for further optimization

Investigation of tetrasubstituted heterocycles reveals hydantoins as a promising scaffold for development of novel antimicrobials with membranolytic properties

Mimics of antimicrobial peptides (AMPs) have been proposed as a promising class of antimicrobial agents. We report the analysis of five tetrasubstituted, cationic, amphipathic heterocycles as potential AMP mimics. The analysis showed that the heterocyclic scaffold had a strong influence on the haemolytic activity of the compounds, and the hydantoin scaffold was identified as a promising template for drug lead development. Subsequently, a total of 20 hydantoin derivatives were studied for their antimicrobial potency and haemolytic activity. We found 19 of these derivatives to have very low haemolytic toxicity and identified three lead structures, 2dA, 6cG, and 6dG with very promising broad-spectrum antimicrobial activity. Lead structure 6dG displayed minimum inhibitory concentration (MIC) values as low as 1 μg/mL against Gram-positive bacteria and 4–16 μg/mL against Gram-negative bacteria. Initial mode of action (MoA) studies performed on the amine derivative 6cG, utilizing a luciferase-based biosensor assay, suggested a strong membrane disrupting effect on the outer and inner membrane of Escherichia coli. Our findings show that the physical properties and structural arrangement induced by the heterocyclic scaffolds are important factors in the design of AMP mimics

Sinteza, spektroskopska karakterizacija i ab initio istraživanje tioanaloga spirohidantoina

Dithioanalogues of cycloalkanespiro-5-hydantoins were prepared by reaction of the respective spirohydantoins with Lawesson’s reagent or P4S10. Cycloalkanespiro-5-(2-thiohydantoins) and cycloalkanespiro-5-(4-hydantoins) were also synthesized from cycloalkanespiro-5-(2,4-dithiohydantoins) via different reaction pathways. The structures of the compounds obtained were verified by 1H, 13C NMR and IR spectroscopy. Quantum-chemical calculations at the ab initio level of molecular nonlinear characteristics were performed. Increase of polarizability α and the second hyperpolarizability γ with enlarging the saturated ring was observed in all the structures studied.Ditioanalozi cikloalkan-spiro-5-hidantoina pripravljeni su reakcijama odgovarajućih spirohidantoina i Lawesson-ovoga reagensa ili P4S10. Sintetizirani su i cikloalkan-spiro-5-(2-tiohidantoini) i cikloalkan-spiro-5- -(4-tiohidantoini), uporabom različitih reakcijskih putova. Strukture dobivenih spojeva potvrđene su 1H, 13C NMR i IR spektroskopijom. Nelinearne molekularne karakteristike predviđene su kvantno-kemijskim računima na ab initio razini. U svim proučavanim strukturama, s povećanjem zasićenog prstena došlo je do porasta polarizabilnosti α i druge hiperpolarizabilnosti γ